1. Field of the Invention
The present invention relates to a recording apparatus for recording information on a recording medium and more particularly relates to a light or optical recording apparatus which produces a modulated light or radiant energy signal for acting on the recording medium.
2. Description of the Prior Art
Typically, prior art light recording apparatus have included a laser light source which provides a light beam and a light modulator which modulates the light beam with an information signal and directs the modulated light beam toward a recording medium, for example, in the form of a recording disc, so that the information signal is recorded on the disc.
Laser light sources employed for use in such light recording apparatus include argon-ion and helium-cadmium lasers. Light modulators conventionally used include electro-optic and acousto-optic modulators in which the light refractive index of a medium within the light modulator is varied on the basis of the intensity of an electric field or the pressure of a sound/wave applied to the light refractive medium, respectively. Light modulators can also control the intensity of the light directed against the recording material so as to compensate for changes in the recording material sensitivity and/or changes in the linear velocity of the recording medium in respect to the modulated light beam, for example, as when the recording medium is a record disc rotated at a constant rotational speed and the light beam is made to scan a spiral path on the disc.
For controlling the light intensity, various devices have been used including optical filters, two electro-optic light modulators, one of which is used to modulate the light signal within the laser light source and the other to control the amount of light emitted from the laser light source, and current modulating means which control a current applied to a laser element within the laser light source. Light or optical recording apparatus incorporating such devices have undesirable features. For example, an optical filter is difficult to be electrically controlled and is unable to reduce noises caused by laser light emission. A device using two electro-optic light modulators can control the amount of light, reduce noise and modulate the signal but at a very high cost and by increasing the complexity of the optical system employed therein. Current modulating means can only be used for an argon-ion laser which restricts the type of laser that can be employed.